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First year of B  hh data: impact of misalignments

First year of B  hh data: impact of misalignments. Jacopo Nardulli & Eduardo Rodrigues Outline Alignment issues [Will treat only B ππ ] 0.01/fb 0.1/fb 0.5/fb What is needed & conclusions  Ongoing studies. Statistics roughly corresponding to 0.01, 0.1 and 0.5/fb.

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First year of B  hh data: impact of misalignments

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  1. First year of B hh data:impact of misalignments • Jacopo Nardulli & Eduardo Rodrigues • Outline • Alignment issues [Will treat only Bππ] • 0.01/fb • 0.1/fb • 0.5/fb • What is needed & conclusions  Ongoing studies

  2. Statistics roughly corresponding to0.01, 0.1 and 0.5/fb • To produce sets corresponding to 0.01, 0.1 and 0.5/fb • we run on Bdπ πDSTs. • At the end we have three sets • 1 set with ~0.01/fb • 1 set with ~0.1/fb • 1 set with ~0.5 /fb • [In DC04 the annual yield was ~36k events, for 2/fb] • We repeat this three times: • Perfect, Software and Hardware alignment

  3. Number of events

  4. Why ?Pattern recognition efficiency • PR efficiencies for “long” tracks • The degradation in finding efficiency is dramatic! • Forward and Match both provide long tracks  Main drop from software to hardware alignment

  5. 0.01/fbσp/p • Perf Align 0.39% • Soft Align  0.4% • - Hard. Align  0.46% • Perf Align 0.39% • Soft Align  0.39% • - Hard. Align  0.43%

  6. 0.01/fbMass distribution • Perf Align: Gauss σ 23MeV • Soft Align Gauss σ 25MeV • - Hard. Align Gauss σ 36 MeV

  7. 0.01/fbProper time • Too little statistics to perform fit • Perf Align • Soft Align • - Hard. Align

  8. 0.1/fbσp/p • Perf Align 0.39% • Soft Align  0.41% • - Hard. Align  0.46% • Perf Align 0.39% • Soft Align  0.41% • - Hard. Align  0.44%

  9. 0.1/fbMass distribution • Perf Align: Gauss σ 23MeV • Soft Align Gauss σ 25MeV • - Hard. Align Gauss σ 43 MeV

  10. 0.1/fbProper time • - Perf Align • Soft Align • - Hard. Align

  11. 0.5/fbσp/p • Perf Align 0.39% • Soft Align  0.41% • - Hard. Align  0.46% • Perf Align 0.39% • Soft Align  0.41% • - Hard. Align  0.45%

  12. 0.5/fbMass distribution • Perf Align: Gauss σ 23MeV • Soft Align Gauss σ 26MeV • - Hard. Align Gauss σ 43 MeV

  13. 0.5/fbProper time • - Perf Align • Soft Align • - Hard. Align

  14. What happens to the physics ? Main problem is significant loss of events  some tracks can probably be recovered with flexible PR algorithms (e.g. Match vs. Forward PR) Momentum and mass resolutions degrade fast as well Software alignment :  If we achieve the precisions we quote, reconstruction and physics performance suffer little Hardware alignment : Mass resolution ~40 MeV is a very serious issue see BsπK as an example Outlook

  15. BsπK Nominal 40 MeV This is with 2/fb • Signal :BsπK • Background : BdπK, separation only through mass resolution • Plot made through smearing studies

  16. Ongoing studiesJ. Nardulli/E. Rodrigues/M.Gersabeck • Start with misalignments on the Bd ππ • Start to look at effects on momentum/mass [IT/OT] • proper time [VELO] • Combined effects of Velo/T-Station misalignments • Cross-check with other decays (BsπK) • Look at B/S ratio • Effects on CP sensitivity • Final effects after introducing (software) re-alignment

  17. Spares

  18. Software/Hardware alignments are 1/5 sigma Sigma: VELO : 3/ 3 / 10 mm --- 1.0 / 1.0 / 0.3 mrad OT : 50 / 0 / 100 mm --- 0.1 / 0.1 / 0.1 mrad IT : 15 / 25 / 50 mm --- 0.1 / 0.1 / 0.1 mrad Alignment details

  19. IT/OT Misalignment for layers Velo Misalignments for sensors Gaussian misalignments with a defined sigma for layers/sensors Alignment details

  20. Why ?Pattern recognition efficiency • PR efficiencies for “long” tracks • The degradation in finding efficiency is dramatic!

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